Note: This article features material from the first edition of Mass Effect: Deception, which BioWare has acknowledged contains discrepancies with other Mass Effect lore. Once revised editions of the book are released, this article will be updated.
Hal McCann is a Cerberus operative introduced in Mass Effect: Deception. McCann was a loyal operative who had served aboard the space station where the Illusive Man had conducted his Reaper technology experiments on Paul Grayson. When the turian strike force attacks the station, McCann survives by playing dead until the turians removed him and other corpses to their ship. He killed both the pilots and took the ship to Omega, where he sold it for money that he hoped to use to get back in contact with Cerberus. Before he could do that, he gambles his money and his freedom away and is eventually sold to a group of batarian slavers.
When the slave ship he is on, the Glory of Khar'shan, unsuccessfully attacks the quarian ship Idenna and is captured itself, McCann is freed and encounters Gillian Grayson and Hendel Mitra. Hiding his affiliation with Cerberus, McCann tells Gillian that her father had been killed and persuades her to look for information on the Citadel, which is where McCann wants to go.
Upon arriving at the space station, Hendel and Gillian bring McCann with them to David Anderson and Kahlee Sanders' apartment which, unbeknownst to them, is being monitored by Cerberus assassin Kai Leng. Leng recognizes McCann and Gillian and informs the Illusive Man, who orders that both be disposed of before they can damage Cerberus. Knowing that McCann is an avid gambler, Leng searches for him in several of the Citadel's clubs and corners him. They fight and McCann manages to prevail due in part to Leng's preexisting injuries, but instead of finishing Leng off or taking the opportunity to escape he stays to gloat. The mistake is fatal; Leng stabs McCann in the foot, then crushes his neck with a baton. Leng leaves McCann's body in a bathroom stall.